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Full text of "Carbon in Drylands: Desertification, Climate Change and Carbon Finance A UNEP-UNDP-UNCCD Technical Note for Discussions at CRIC 7, Istanbul, Turkey, 03-14 November, 2008. Prepared on behalf of UNEP by UNEP-WCMC"

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Carbon in Drylands: Desertification, Climate 
Change and Carbon Finance 

A UNEP-UNDP-UNCCD Technical Note for 
Discussions at CRIC 7, Istanbul, Turkey - 03-14 
November, 2008 

Prepared on behalf of UNEP by UNEP-WCMC 

Authors: Kate Trumper, Corinna Ravilious and Barney Dickson 

31 s1 October 2008 

Disclaimer: The contents of this report do not necessarily reflect the views or policies 
of UNEP-WCMC or contributory organisations. The designations employed and the 
presentations do not imply the expressions of any opinion whatsoever on the part of 
UNEP-WCMC or contributory organisations concerning the legal status of any 
country, territory, city or area or its authority, or concerning the delimitation of its 
frontiers or boundaries. 

Technical Note: Carbon in drylands - Desertification, 
climate change and carbon finance 


Drylands cover about 40% of the Earth's land surface, excluding Antarctica and 
Greenland, and are home to more than two billion people (WRI 2002). They are 
susceptible to desertification, land degradation and drought (DLDD) and their 
populations, agriculture and ecosystems are vulnerable to climate change and 
variability. The United Nations Convention to Combat Desertification (UNCCD), one 
of the three 'Rio' conventions born out of the 1992 United Nations Conference on 
Environment and Development (UNCED). aims to address these issues and 
emphasises action to promote sustainable development at the community level. 

The other Rio conventions are the United Nations Framework Convention on Climate 
Change (UNFCCC) and the Convention on Biological Diversity (CBD). The areas of 
interest of the three Conventions are closely linked and each has accepted the need to 
work in concert. One area of joint interest is that of the uptake of carbon dioxide from 
the atmosphere by plants and its storage in ecosystems. It is perhaps the only 
practicable way of removing carbon dioxide from the atmosphere in the short term 
and therefore one of the few options for addressing its existing carbon load, as distinct 
to slowing future loading by reducing current and future emissions. Most attention so 
far has focussed on carbon sequestration by tropical forests. More recently, some have 
argued for a more holistic approach to terrestrial carbon (The Terrestrial Carbon 
Group, 2008). This paper reviews the potential for carbon sequestration in dryland 
ecosystems, which includes forests, but also covers other habitats, such as grasslands, 
and, importantly, soils. It also considers ways in which carbon storage in drylands 
affects land degradation issues. 

Carbon storage in drylands 

Plants take up carbon dioxide from the atmosphere and incorporate it into plant 
biomass through photosynthesis. Some of this carbon is emitted back to the 
atmosphere but what is left — the live and the dead plant parts, above and below 
ground — make up an organic carbon reservoir. Some of the dead plant matter is 
incorporated into the soil in humus, thereby enhancing the soil organic carbon pool. 

Plant biomass per unit area of drylands is low (about 6 kilograms per square meter) 
compared with many terrestrial ecosystems (about 10-18 kilograms). But the large 
surface area of drylands gives dryland carbon sequestration a global significance. In 
particular, total dryland soil organic carbon reserves comprise 27% of the global soil 
organic carbon reserves (MA 2005). The soil properties, such as the chemical 
composition of soil organic matter and the matrix in which it is held, determine the 
different capacities of the land to act as a store for carbon that has direct implications 
for capturing greenhouse gases (FAO 2004). The fact that many of the dryland soils 
have been degraded means that they are currently far from saturated with carbon and 
their potential to sequester carbon may be very high (Farage et al. 2003). 



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The map above shows how the density of carbon stored, that is, the mass of carbon 
per hectare, varies throughout drylands. The carbon densities are derived from two 
global datasets: the carbon stock in biomass is from a map based on IPCC Tier-1 
Methodology using global land cover data. (Ruesch & Gibbs, in review); soil carbon 
is from Global Soil Data Products CD-ROM. (IGBP-DIS 2000). The delineation of 
drylands is from UNEP-WCMC's map of areas of relevance to the CBD's programme 
of work on dry and sub-humid lands (UNEP-WCMC 2007). The UNCCD defines 
drylands according to an aridity index: the ratio of mean annual precipitation to mean 
annual potential evapotranspiration. The CBD definition of 'drylands' used within its 
Programme of Work on Dry and Subhumid Lands (UNEP/CBD/SBSTT A/5/9) differs 
from the UNCCD definition described above in two ways: 

i. It includes hyperarid zones (CCD does not) (UNEP/CBD/SBSTTA/5/9), 
which represent approximately 6.6 percent of the Earth's land surface. 

ii. Major vegetation types are used to define dryland areas in addition to those 
defined according to the aridity index (UNEP/CBD/SBSTTA/5/9). 

Table 1 gives a breakdown of the carbon stored in each region in drylands. Figures for 
the total carbon stock in each region are from Campbell et al. (2008) and are derived 
from the same data as the dryland figures. Estimates of carbon stored in each region 
are sensitive to changes in land cover type. Therefore for detailed regional or national 
purposes, it will be necessary to refine global land cover data with more detailed local 
data. Nevertheless, this global overview shows that dryland carbon storage accounts 
for more than one third of the global stock. In some regions, such as the Middle East 
and Africa, a very high proportion of carbon is in drylands, so any sequestration 
measures there would need to address dryland ecosystems. Even in regions such as 
Africa and South Asia, where moist forests contain a lot of carbon, dryland carbon 
storage is still significant. 

Table 1. Comparison of total and drylands carbon stocks in regions of the wo rld 



Total carbon 
stock per 
region (Gt) 

stock in 

Share of 
carbon stock 
held in 
drylands (%) 


North America 








Central America & 





South America 










North Eurasia 










Middle East 





South Asia 





East Asia 





South East Asia 





Australia/New Zealand 











Land degradation and carbon emissions 

According to the Millennium Ecosystem Assessment, "some 10-20% of the world's 
drylands suffer from one or more forms of land degradation. Despite the global 
concern aroused by desertification, the available data on the extent of land 
degradation in drylands (also called desertification) are extremely limited. In the early 
1990s, the Global Assessment of Soil Degradation, based on expert opinion, estimated 
that 20% of drylands (excluding hyper-arid areas) were affected by soil degradation. 
A study based on regional data sets (including hyper-arid drylands) derived from 
literature reviews, erosion models, field assessments and remote sensing found much 
lower levels of land degradation in drylands. Coverage was not complete, but the 
main areas of degradation were estimated to cover 10% of global drylands." The MA 
estimated that the true level of degradation lay somewhere between the 10% and 20% 
figures. (MA 2005). The Land Degradation Assessment in Drylands (LADA) project, 
funded by the Global Environmental Facility (GEF) and carried out by the Food and 
Agriculture Organization of the United Nations (FAO) is drawing together 
information about degradation and developing ways of assessing the extent of land 
degradation and its impacts. 

Land use change and degradation are important sources of greenhouse gases globally, 
responsible for about 20% of emissions (IPCC, 2007). Land degradation leads to 
increased carbon emissions both through loss of biomass when vegetation is 
destroyed and through increased soil erosion. Erosion leads to emissions in two ways: 
by reducing primary productivity, thereby reducing soils 1 potential to store carbon and 
through direct losses of stored organic matter. Although not all carbon in eroded soil 
is returned to the atmosphere immediately, the net effect of erosion is likely to be 
increased carbon emissions (MA, 2005). 

There have been a number of estimates of the rate of carbon emissions due to land 
degradation in drylands at different scales. At the global scale, Lai (2001) estimated 
that dryland ecosystems contribute 0.23 - 0.29 Gt of carbon a year to the atmosphere, 
which is about 4% of global emissions from all sources combined (MA 2005). In 
China, degradation of grassland, particularly on the Qinghai-Tibetan Plateau, has led 
to the loss of 3.56 Gt soil organic carbon over the last 20 years. It is estimated that 
the soils of China overall now act as a net carbon source, with a loss of 2.86 Gt in the 
same period (Xie et al., 2007). It is therefore vital from a climate perspective that this 
region is managed to enhance carbon sequestration (Xu et al., 2004) and further study 
is clearly required in this area (ESPA China 2008). 

Grace et al. (2006) reviewed carbon fluxes in tropical savannas. They found that 
carbon sequestration rates in these ecosystems may average 0.14 tonnes carbon per 
hectare per year or 0.39 tonnes carbon per hectare per year. They concluded that "if 
savannas were to be protected from fire and grazing, most of them would accumulate 
substantial carbon and the sink would be larger. Savannas are under anthropogenic 
pressure, but this has been much less publicized than deforestation in the rain forest 
biome. The rate of loss is not well established, but may exceed 1% per year, 
approximately twice as fast as that of rain forests. Globally, this is likely to constitute 
a flux to the atmosphere that is at least as large as that arising from deforestation of 
the rain forest." 

As well as contributing to greenhouse gas emissions, drylands are themselves 
vulnerable to the effects of climate change and the impacts of climate change in these 
areas may lead in turn to further carbon emissions. Any further failure of plant growth 
due to increased temperatures would further reduce carbon inputs to the soil, 
accelerating its degradation. Smith et al point out that "even partial loss of vegetation 
integrity could make soils more vulnerable to degradation through other agents such 
as grazing and cultivation.' (Smith et al 2008) 

Climate change mitigation through addressing DLDD 

Addressing land degradation in dryland ecosystems presents two complementary 
ways of mitigating climate change. First, by slowing or halting degradation, 
associated emissions can be similarly reduced. Second, and arguably of greater 
significance, changes in land management practices can lead to greater carbon 
sequestration, that is, to removing carbon from the atmosphere. In general, the carbon 
storage potential of dryland ecosystems is lower than for moist tropical systems, but 
the large area of drylands means that overall they have significant scope for 

Managing drylands for carbon sequestration 

Since carbon losses from drylands are associated with loss of vegetation cover and 
soil erosion, management interventions that slow or reverse these processes can 
simultaneously achieve carbon sequestration. There is a wide range of strategies to 
increase the stock of carbon in the soil. Examples include enhancing soil quality, 
erosion control, afforestation and woodland regeneration, no-till farming, cover crops, 
nutrient management, manuring and sludge application, optimal livestock densities, 
water conservation and harvesting, efficient irrigation, land-use change (crops to 
grass/trees), set-aside, agroforestry, and the use of legumes (FAO 2004, Lai 2004, 
Smith 2008). 

There is a growing interest in assessing the carbon sequestration potential of such 
strategies quantitatively. Using a modelling approach, Farage et al (2007) found the 
most effective practices for increasing soil carbon storage were those that maximised 
the input of organic matter, particularly farmyard manure (up to 0.09 tonnes C per 
hectare per year), maintaining trees (up to 0.15 tonnes C per hectare per year) and 
adopting zero tillage (up to 0.04 tonnes C per hectare per year (Farage et al 2007). 

Tiessen et al. (1998) reviewed data on carbon and biomass budgets under different 
land use in tropical savannas and some dry forests in West Africa and North-Eastern 
Brazil. They found that improvements in the carbon sequestration in these semi arid 
regions depended on an increase in crop production under suitable rotations, improved 
fallow and animal husbandry, and a limitation on biomass burning. Use of fertilizer 
was required for improved productivities but socioeconomic constraints largely 
prevented such improvements, resulting in a very limited scope for changes in soil 
carbon management. 

Increasing carbon stocks in the soil increases soil fertility, workability, water holding 
capacity, and reduces erosion risk and can thus reduce the vulnerability of managed 
soils to future global warming (Smith. 2008). However, hidden costs also need to be 

considered, such as the addition of mineral or organic fertilizer (especially nitrogen 
and phosphorus) and water, which would need significant capital investment (MA 

Estimates of dryland carbon sequestration potential 

Several studies have attempted to assess the potential for carbon sequestration in 
drylands. Considering all drylands ecosystems, Lai (2001) estimated that they had the 
potential to sequester up to 0.4-0.6 Gt of carbon a year if eroded and degraded 
dryland soils were restored and their further degradation were stopped. In addition, he 
suggested that various active ecosystem management techniques, such as reclamation 
of saline soils, could increase carbon sequestration by 0.5-1.3 Gt of carbon a year. 
Squires et al (1995) estimated similar figures. Keller and Goldstein (1998) reached the 
slightly higher figure of 0.8 Gt of carbon per year using estimates of areas of land 
suitable for restoration in woodlands, grasslands, and deserts, combined with 
estimates of the rate at which restoration can proceed. 

Other studies have examined specific ecosystems in particular locations. For example, 
Glenday (2008) measured forest carbon densities of 58 to 94 tonnes C/ha in the dry 
Arabuko-Sokoke Forest in Kenya and concluded that improved management of wood 
harvesting and rehabilitation forest could substantially increase terrestrial carbon 
sequestration. Farage et al. (2007) used soil organic matter models to explore the 
effects of modifying agricultural practices to increase soil carbon stocks in dryland 
farming systems in Nigeria, Sudan and Argentina. Modelling showed that it would be 
possible to change current farming systems to convert these soils from carbon sources 
to net sinks without increasing farmers' energy demand. The models indicated that 
annual rates of carbon sequestration of 0.08-0.17 tonnes per ha per year averaged over 
the next 50 years could be obtained. 

Despite these studies, significant gaps in knowledge remain. Better information is 
needed on the impact of land use changes and desertification on carbon sequestration 
and the cost-benefit ratio of soil improvement and carbon sequestration practices for 
small landholders and subsistence farmers in dryland ecosystems (MA 2005). 

Linking drylands development and carbon markets 

There are two markets for carbon sequestration: a) the compliance market governed 
by the United Nations Framework Convention on Climate Change (UNFCCC) 
through its Kyoto Protocol and b) the voluntary market. The role of the natural 
biosphere in climate change mitigation is recognised in the UNFCCC through Land 
Use Land Use Change and Forestry (LULUCF). 

Annex I Parties, under Article 3.3 of the Kyoto Protocol, can use "direct human- 
induced land-use change and forestry activities, limited to afforestation, reforestation 
and deforestation since 1990, measured as verifiable changes in carbon stocks, " to 
meet emissions reductions targets. In addition, they can elect Forest Management, 
Grassland Management, Cropland Management, and Revegetation for inclusion in the 
accounting process. There are calls by some to include all lands and associated 
processes in the LULUCF, rather than the narrow activities specified above. 

The rules for LULUCF were only set after emission reduction targets had been 
agreed. This has been viewed as a limitation, as in effect land use activities 'offset' 
emissions in other sectors, rather than acting as an integral part of the mitigation 
portfolio. Issues still remain over the permanence of sequestration activities as 
management changes or natural disturbances can quickly release any carbon 

The opportunities for Non Annex 1 countries to participate in such activities is also 
limited, and restricted to the Clean Development Mechanism (CDM); where Annex I 
countries can gain carbon credits through activities in developing countries. CDM 
activities are restricted to Afforestation, Reforestation and Deforestation activities, 
and can make up only 1% of the emissions reduction portfolio for Annex I countries. 

As yet few forestry-based carbon sequestration activities have been funded through 
the CDM, partly because of concerns about additionality, permanence and leakage. 
Voluntary markets have developed their own regulations and protocols, and are the 
only outlet for reduced deforestation programmes at the moment. 

However, the UNFCCC is considering introducing a financial mechanism to reduce 
emissions from deforestation and forest degradation (REDD) in developing countries. 
There is still a great deal of uncertainty about the form of the mechanism, not least 
how it will be funded. One option is to do so though a specific fund, another is a 
market-based mechanism that would allow developing countries to sell carbon credits 
on the basis of successful reductions in emissions from deforestation and forest 
degradation. A market-based mechanism is expected to generate a much greater 
supply of funds; one estimate, based on a relatively low carbon price of U.S. $10 per 
ton and an estimate of individual countries' ability to slow deforestation, suggests a 
potential market of U.S. $1.2 billion a year (Niles et al, 2002). 

The United Nations Collaborative Programme on Reducing Emissions from 
Deforestation and Forest Degradation in Developing Countries (UN-REDD 
Programme) is a collaboration between FAO, UNDP and UNEP. It is aimed at 
"tipping the economic balance in favour of sustainable management of forests so that 
their formidable economic, environmental and social goods and services benefit 
countries, communities and forest users while also contributing to important 
reductions in greenhouse gas emissions". Its immediate goal is to assess whether 
carefully structured payment structures and capacity support can create the incentives 
to ensure actual, lasting, achievable, reliable and measurable emission reductions 
while maintaining and improving the other ecosystem services forests provide. The 
UN-REDD programme has nine initial pilots, two of which - Tanzania and Zambia - 
are dryland woodland countries. 

The potential scale of funding available through a market-based REDD has drawn 
attention to both its potential for achieving other benefits simultaneously and the risk 
of displacing degradation into areas that may have low carbon storage potential, but 
that are valuable in other ways (Miles and Kapos 2008). There are technical and 
statistical challenges of measuring changes in above and belowground carbon stocks 
over large areas in drylands with the required accuracy, and further research is 
required to demonstrate the feasibility of large area measurement schemes. The pros 

and cons of carbon accounting at different scales (e.g. individual land user, watershed, 
national level) and the associated transaction costs in administering such schemes also 
still need to be evaluated. 

REDD is applicable to forested ecosystems only, but other carbon markets may 
include projects based in other ecosystems, depending on their carbon sequestration 
potential. Regardless of the market, the price of carbon strongly influences whether 
interventions to manage land degradation and carbon sequestration simultaneously are 
cost effective. At present, the price of soil organic carbon, for example, is low, at 
about $1 per tonne, so only low-cost interventions are likely to be cost effective for 
land managers. For example. Smith (2008) concluded that there was technically the 
potential to increase soil organic carbon stocks by about 1-1.3 Gt per year. However, 
he found that if carbon prices were less than US$20 per tonne it would only be 
economically feasible to increase soil carbon stocks by up to 0.4 Gt carbon per year. 
At higher carbon prices, costlier interventions may generate sufficient revenue 
through carbon credits to be worth undertaking. 

The important questions for drylands, then, are first to identify areas, forest or 
otherwise, where the carbon storage potential is great enough to attract carbon finance 
based on that alone and second to consider whether REDD and other mechanisms 
could prioritise schemes that also delivered co-benefits such as watershed or erosion 

The studies referred to in this technical note indicate that, although carbon density 
(tonnes of carbon stored per hectare) of drylands is low, the total amount stored can 
be large as the areas involved are large. As such, interventions that increase the 
amount of carbon stored in drylands, particularly those that are relatively low cost, 
may be attractive to carbon markets. Tropical dry forests can store significant 
amounts of carbon (ECCM 2007) so REDD may be a suitable finance mechanism for 
anti-degradation measures in these ecosystems, particularly in dryland nations that do 
not have carbon-rich moist forest. However, it would be helpful to have more 
information on the characteristics of dryland forest and their carbon storage potential, 
as well as greater clarity of the form that REDD mechanism will take, to estimate the 
likely scale finance available for UNCCD-relevant forests. 

It is clear that dryland carbon sequestration, particularly in soils, can provide other 
ecosystem and social benefits such as as the rebuilding of the biophysical foundations 
of a sustainable natural environment - biodiversity, forests, livestock, soils, water, 
natural ecosystems - thus increasing productivity, improving water quality, and 
restoring degraded soils and ecosystems. In its 2004 report on carbon sequestration in 
dryland soils, the FAO concluded that "actions for soil improvement through carbon 
sequestration are a win - win situation where increases in agronomic productivity may 
help mitigate global warming, at least in the coming decades, until other alternative 
energy sources are developed" (FAO 2004). 


Sustainable land management practices that address desertification, land degradation 
and drought (DLDD) in drylands can also have significant carbon sequestration 
potential, particularly where they increase the organic carbon content of soils. As Lai 
(2004) pointed out, the carbon sink capacity of tropical dryland soils is high in part 

because they have already lost a lot of carbon. Restoring that carbon offers long-term 
sequestration and can improve crop yields and increase ecosystems' resilience to 
future climate variability. Indeed, the UNCCD's 10 year strategic plan (10YSP) 
recognises the links between DLDD and climate change. One indicator of the plan's 
strategic objective 3 "to generate global benefits through effective implementation of 
the UNCCD" is to achieve an "increase in carbon stocks (soil and plant biomass) in 
affected areas" (indicator S-6). 

However, weak institutions, limited infrastructure and resource-poor agricultural 
systems often limit the capacity to address soil carbon and DLDD. Carbon markets 
offer a possible way of financing measures to do so in some areas. However, for 
significant carbon finance to be channelled to dryland ecosystems, it may be 
necessary that market mechanisms allow prioritisation or a premium for schemes that 
offer other benefits. Both forest and non-forest ecosystems have carbon sequestration 
potential, but the price of carbon traded in the voluntary market is often too low to 
influence land management practices at present. The 10YSP has already set a strategic 
objective (Strategic objective 4) of mobilising resources to support implementation of 
the Convention through building effective partnerships between national and 
international actors. Work that encourages national and international carbon markets 
to consider co-benefits in terms of ecosystem serves as well as carbon is in line with 
this objective. 

Given that soil carbon sequestration has much to offer climate change mitigation, land 
and livelihood protection and resilience to climate change, but that actions to enhance 
it may be hampered by lack of finance, lack of data and perhaps capacity to 
implement changes, it is all the more important that policies and institutions 
addressing these issues should work co-operatively, as set out in 10YSP. 


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